I. Field of the Invention
The present invention relates generally to direct injection internal combustion engines and, more particularly, to an apparatus for reducing the transmission of vibration from the fuel rail to the engine head in direct injection engines.
II. Description of Material Art
Direct injection internal combustion engines, i.e. engines in which the fuel injector injects the fuel directly into the combustion chamber rather than upstream from the inlet valve, exhibit several advantages over the more conventional port-fuel injected internal combustion engines. Most notably, direct injection engines enjoy increased fuel economy over the other types of internal combustion engines. Direct injection internal combustion engines, however, do present special challenges for engine manufacturers and, in particular, automotive engine manufacturers.
One disadvantage of the previously known direct engine internal combustion engines is that such engines exhibit excessive noise which is particularly evident at low engine speeds. Such noise, furthermore, is directly attributable to the fuel system.
The fuel system for a direct injection engine typically comprises a fuel rail which is secured to the engine head. At least one, and more particularly several, fuel injectors are attached to and suspended from the fuel rail. A portion of each fuel injector extends through an opening in the engine head so that an end of the fuel injector is open to an internal combustion chamber for the engine. In operation, pressurized fuel from the fuel rail passes through the fuel injector and into the internal combustion engine as desired.
In order to properly supply fuel to the combustion chambers during the operation of the engine, the pressure in the fuel rail must necessarily be very high and significantly higher than previously known fuel injected engines that were not direct injection engines. In order to supply this pressurized fuel to the engine, a piston pump in a fuel pump is typically reciprocally driven by a cam having at least two or more typically three or four lobes. These lobes all contact the piston pump, usually through a roller. Upon rotation of the cam, the lobes cause the piston to move reciprocally against the force of a compression spring within the pump housing which is fluidly connected to and supplies pressurized fuel to the fuel rail.
The fuel pump also includes an inlet valve which is movable between an open and closed position by an electric coil or solenoid. In its open position, fuel flows to or from the fuel pump chamber within the pump housing through the valve port. Conversely, when the valve is moved to its closed position, the piston during the pump cycle pumps pressurized fuel through a check valve and into the fuel rail for the engine.
The operation of the fuel pumps for a direct injection engine, however, causes significant engine noise, especially at low engine speeds. The high pressure pulsation of fuel through the fuel injection induces vibration of the fuel injector which, in turn, is transmitted to the engine head and causes noise.